The present invention relates to a fuser member and method for fusing toner images in electrostatographic reproducing, including digital and image on image, apparatuses. The fuser member is especially useful for fusing color images. More specifically, the present invention relates to apparatuses directed towards fusing toner images using a fuser member having a fluoropolymer layer with fillers that promote thermal conductivity such as a) aluminum oxide of varying particle sizes and b) silicone materials. In a preferred embodiment, aluminum oxide of at least two different particle sizes is dispersed or contained in the fluoropolymer layer, along with crosslinked and/or cured silicone particles. In a particularly preferred embodiment, the fuser member has an outer layer comprising a fluoropolymer, silicone particle, and alumina particles of at least two different sizes.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes it to be firmly bonded to the support.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members.
Known fuser members include those with outer layers of polytetrafluoroethylene to which a release agent such as silicone oil has been applied. More recently, silicone rubber and fluoroelastomers such as VITON.RTM. (Trademark from E.I. DuPont) coated fuser members have been used to enhance copy quality. The following are known fuser members.
U.S. Pat. No. 5,595,823 discloses a fuser member having a layer including a cured fluorocarbon random copolymer having subunits of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene and having aluminum oxide filler along with alkali metal oxides and/or alkali metal hydroxide fillers incorporated into the fuser member layer. A polydimethylsiloxane and mercapto fuser oil are also disclosed.
U.S. Pat. No. 4,711,818 discloses a fuser member having a core, and an outer layer comprising a crosslinked product of a mixture of at least one addition curable vinyl terminated or vinyl pendant polyfluoroorganosiloxane, heat stabilizer, filler, crosslinking agent and crosslinking catalyst. The filler may be calcined or tabular alumina.
U.S. Pat. No. 5,729,813 discloses a fuser member having a core and a surface layer comprising a fluoroelastomer and an alumina filler present in an amount of from about 30 to about 55 parts by weight, which corresponds to from about 11 to about 20 volume percent alumina. There may be present an intermediate silicone layer.
U.S. Pat. No. 5,292,606 discloses a fuser member having a base cushion layer comprising polydimethyl siloxane and at least one outer layer, wherein zinc oxide is present in the base cushion layer. The reference discloses that the zinc oxide particles can be replaced with aluminum oxide particles in a preferred amount of 8 to 40 volume percent.
U.S. Pat. No. 4,257,699 discloses a fuser member having a core and two outer layers. Example 1 discloses a base member, a silicone intermediate layer containing aluminum oxide particles, and an outer silicone rubber layer containing silver particles.
For developing color images, several layers of different color toner are deposited on the latent image resulting in extra thickness (higher toner pile height) of unfused toner on a color image. Increased thermal conductivity is necessary in order to provide higher temperatures for fusing the increased amount of toner, without excess use of energy. Improved release, either by extra release agent and/or improved surface release properties, is necessary for improving toner release due to the increase in toner used for color developing. Further, extended dwell time at the nip is necessary to ensure complete toner flow. In addition, a conformable fuser member is necessary in order to ensure sufficient release and stripping. Moreover, a smooth surface is necessary in order to provide color images with preferred increased gloss which is normally customer preferred for color prints.
However, known fuser members do not provide the same quality for colored images as they do for black and white images. Therefore, it is desired to provide a fuser member, preferably in combination with a pressure member, wherein high quality color prints or copies are produced. Particularly, it is desired to provide fuser members demonstrating excellent results at the higher temperatures necessary in color fusing by possessing increased thermal conductivity and release properties. It is further desirable to provide fuser members possessing smooth, conformable layers having a long-dwell nip and a decrease in swell. Moreover, it is desirable to provide fusing layers which are more easily processable.